Gravure printing machines, dry laminating machines, coating machines, and the like have a drying oven as a principal constitution part. For example, in multicolor gravure printing machines, ink dissolved in a solvent is applied to a substrate by a gravure roll in the first color printing unit, followed by evaporating the solvent in a drying oven to solidify the ink alone on the substrate and cooled, and then transferred to the second color printing unit. Printing is carried out through similar processes in the second and thereafter printing units up to the final printing unit, to complete the substrate provided with multi-color printing, and finally wound up.
Moreover, in dry laminating machines, to unwound substrate A, an adhesive dissolved in a solvent is applied by a gravure roll, followed by evaporating the solvent in a drying oven, a substrate B is superimposed on the face where the adhesive has been applied, and pressed to form a laminate, and wound up. In coating machines, a coating solution dissolved in a solvent is applied to a substrate by a gravure roll, followed by evaporating the solvent in a drying oven, cooled, and then wound up.
The drying ovens employed in the above respective machines are constructed by almost similar mechanism. That is, in the drying ovens, a plurality of guide rolls are provided, and the substrate to which a liquid agent has been applied is dried by blowing hot air with being guided by the guide rolls. While, the opposite side of the substrate to which the liquid agent has been applied is allowed to contact with the guide rolls, and the side on which the liquid agent has been applied is dried by heat by blowing hot air.
Recently, printings and laminatings are being transferred to aqueous gravure printing and aqueous dry laminating, where solvent is not used, due to the problems of bad smell while working, working atmosphere, residual solvent odor, reduction of CO2 as a remedy for global warming caused by oil solvent (e.g., see Patent Documents 1-6).